Aim: To assess lung function abnormalities and bronchodilator response (BR) among preschool children with recurrent wheezing using spirometry and specific resistance (sRaw).
An observational prospective study was designed with healthy and recurrent wheezing children aged 3 to 6 years, recruited from Vall d’Hebron and Donostia, San Sebastian, Pediatric Pulmonology Units. Children were classified according to wheeze phenotype (ERS Task Force 2008). sRaw was measured using sReff by a single step procedure. Z-scores were calculated with the equations from Asthma UK initiative (Eur Respir J 2010) and GLI (Quanjer, Eur Respir J 2012). BR was assessed as the increase in FEV1, FEV0.75, FEV0,5, FEF 25-75 or decrease in sReff,15 minutes after inhalation of 400 mcg salbutamol. Manoeuvres were repeteated after 6 months. One hundred and twenty six children were tested. Thirty four healthy controls, and 92 wheezers. Eighty six children (68.6%) performed technically acceptable and reproducible spirometry manoeuvres during the first visit and 102 (81.0%) satisfactory sRaw measurements. According to age, 10 (38.5%) 3-year-old preschoolers performed correctly the basal spirometry . 22 (57.9%) 4-year-olds and 54 (86%) preschoolers aged 5 and 6 years did so too. Only the manouevres with correct onset, correct and reproducible curve were considered valid. While for sRaw just the maneuvers with 6 quality points were analyzed. The older preschoolers performed significantly better spirometric and sRaw maneuvers. Preschoolers with wheezing had significantly lower baseline values for all spirometric variables except for FVC, while there was no difference in sRaw values. But those presenting worse respiratory symptoms according to the pediatric and GEMA classification of asthma obtained significantly increased values of sRaw. Preschool wheezing children, presented a significant increase in FEV1, FEV0,75, FEV0,5. We considered significant BR: FEV1 (+ 11.2%), FEV0,75 (+13.1%), FEV0,5 (+ 15.9%), and FEF25-75 (+40.8 %). No control showed significant BD test. In the asthma group, the percentage of positivity ranged from 17.2% for FEV0,5 to 27.3% for FEV1. The bronchodilator test assessed by sRaw did not differentiate children with asthma from controls.
Spirometric indices are more sensitive than specific resistance measurement to detect abnormalities in basal lung function and BR in wheezing preschool children.
As a conclusion, the study of lung function in the group of three to six years of age is feasible with both forced spirometry and sRaw. Preschool children are able to correctly perform forced spirometric maneuvers allowing the use of FEV1, FEV0,75, FEV0,5. The study of baseline lung function and bronchodilator response in preschool asthma is more sensitive with spirometric variables.